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MOSUL, Iraq, April 22 (Reuters) - Gunmen shot dead 23 factory workers from an ancient minority sect in an apparent revenge killing in the northern Iraqi city of Mosul on Sunday, police and hospital sources said.

Brigadier-General Mohammed al-Waggaa said the gunmen stopped the vehicle, forced the textile factory workers out of a minibus and gunned them down in the eastern al-Nour district of Mosul, 390 km (240 miles) north of Baghdad, Iraq's third-largest city.

A source at a local hospital said 23 people were killed and three were seriously wounded.

Waggaa said the execution-style killing appeared to be in retaliation for an incident in which a Yazidi woman was stoned to death several weeks ago for converting to Islam. He said the workers were found near a mosque in the same area.

Another police source who declined to be named confirmed the incident and said the woman had fallen in love with a Muslim man and ran away with him a few months ago.

Police then detained the couple, kept the man in jail and freed the woman after receiving assurances from her family she would not be harmed.

According to the source, members of the Yazidi community decided they had to "cleanse the shame", and stoned the woman to death.

One witness said he saw a mobile phone video of the stoning. The video, which was a few minutes long, showed a group of men beating, kicking and hitting a woman with large blocks of cement.

Yazidis are members of a pre-Islamic Kurdish sect and live in northern Iraq and Syria.

Yazidis in Iraq say they have often faced discrimination because the chief angel they venerate as a manifestation of God is often identified as the fallen angel Satan in biblical terminology.

Yazidis, who say they suffered massacres during the secular rule of Saddam Hussein, also believe God created good and evil in the world.

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